The incorporation of fillers in the manufacture of rubber and plastic products is well-known in the industry. For example, the incorporation of carbon black in tire treads is widely used for improving wear characteristics. Elsewhere, colorants are incorporated into polyvinyl chloride and clays are incorporated into polymer composites.
In some instances, it is desirable to treat these fillers with agents, or binders, to impart further benefits. For example, these binders can reduce the generation of airborne filler dust and can also provide easier conveyance of the filler material. This treatment can also impart different surface characteristic to the binder to allow ease of dispersion into other media or to enhance or reduce interactions between components.
U.S. Pat. No. 2,850,403 discloses the use of carbohydrates (e.g. sugar, molasses, soluble starches, saccharides and lignin derivatives) as pellet binders. Likewise, U.S. Pat. No. 3,844,809 discloses the reduction in pellet dust levels partially through the use of molasses as a co-binder. These binders can form beads or pellets with the filler (such as carbon black).
Another conventional method for reducing the generation of airborne filler dust is mixing the carbon black with a latex. One example of this is U.S. Pat. No. 2,457,962, which discloses methods of beading carbon black with a latex as a wetting agent to improve the handling properties of the carbon black and dispersion of the carbon black in rubber. In one method disclosed therein, carbon black beads are formed by wetting the carbon black with latex and then agitating the mixture in a conventional carbon black pelletizer. The '962 patent discloses that the rubber content of the latex beaded carbon black should range from 5% to 20% by weight of the beaded carbon black.
In another example where a latex was utilized, U.S. Pat. No. 5,168,012 discloses carbon black beads made by a process generally including the steps of adding a latex comprising an elastomer to a carbon black filler and beading the carbon black powder and the latex in a carbon black beading apparatus. There, the latex is added to the carbon black in an amount sufficient to form beaded carbon black and the latex comprises the elastomer in an amount between 0.5% and 5% by weight of the beaded carbon black. The individual aggregates of carbon black particles become associated with latex and the elastomer is distributed substantially throughout the resulting beaded carbon black. The latex-treated carbon black beads are then preferably dried at a temperature sufficiently low to prevent decomposition or gelling of the elastomer.
Another example of using a latex is U.S. Pat. No. 8,586,651, where a method of producing an elastomer composite is disclosed. The method therein generally discloses the steps of combining a first fluid comprising elastomer latex with a second fluid comprising particulate filler; causing the elastomer latex to coagulate, thereby forming masterbatch crumb; bringing the masterbatch crumb to a desired water content, thereby forming a dewatered coagulum; removing water from the dewatered coagulum by subjecting the dewatered coagulum to mechanical energy, thereby causing the dewatered coagulum to heat as a result of friction, while allowing the dewatered coagulum to achieve a desired temperature and water content percentage, thereby producing a masticated masterbatch; and subjecting the masticated masterbatch to additional mechanical energy while further reducing the water content.